Conductive polymers are used in various applications such as conductive coating materials, antistatic agents, electromagnetic wave shielding materials, solid electrolytes, transparent conductive materials, battery materials, capacitor materials, sensor materials, conductive adhesives, electrophotographic materials, photosensitive members, and transfer members. Among the conductive polymers, polythiophene, polypyrrole, polyaniline, polyacethylene, polyphenylene, poly(p-phenylene vinylene), polyacene, polythiophene vinylene, and the like are known as conjugated conductive polymers to date.
Also, a technology is known in which a conjugated conductive polymer is doped with a polyanion such as polystyrene sulfonate (hereinafter also referred to as “PSS”) as a counter anion in order to improve conductivity. In particular, PEDOT-PSS, in which poly(3,4-ethylenedioxy thiophene) (hereinafter also referred to as “PEDOT”) is used as a conjugated conductive polymer and PSS is used as a counter anion, can be obtained as an aqueous dispersion of a conductive polymer having excellent conductivity, and has excellent transparency and stability as well.
As a method for producing such a dispersion of a conjugated conductive polymer in which a polyanion is concomitantly present, for example, PTL 1 discloses subjecting a monomer that is to be a constitutional unit of a conjugated conductive polymer to oxidative polymerization in the presence of a polyanion and an organic sulfonic acid. PTL 2 discloses subjecting 3,4-ethylenedialkoxy thiophene to oxidative polymerization in the presence of a polyacid.
According to PTL 3, a low-viscosity dispersion containing polythiophene and PSS can be prepared in a short reaction time by polymerization through ultrasonic irradiation.